A modern automobile has numerous electronic control units (ECUs) configured to control various vehicle subsystems, such as the engine, transmission, airbags, antilock braking, cruise control, electric power steering, audio systems, windows, doors and mirror adjustments, to name but a few. Some of these subsystems are independent, while others need to exchange data among themselves during the normal operation of the vehicle. For example, the engine needs to tell the transmission the engine speed, and the transmission needs to tell other modules when a gear shift occurs. When an ECU fails or is operational but faulty, the vehicle may exhibit poor performance or be completely disabled. The problem, however, may not originally stem from the ECU itself, but rather a ground fault on the communications network that interconnects the ECUs. In other words, there may be a fault on a communication line rather a fault with the ECU itself. Often times ground faults, which can be difficult to detect even using service station diagnostics, can manifest as ECU faults. Consequently, service stations sometimes unnecessarily replace ECUs in an attempt to determine and solve the problem.
The system and method described hereinafter reduces troubleshooting time, avoids unnecessary ECU replacement, and decreases repeated repair visits by detecting and isolating ground faults prior to an ECU failure.